Filter cigarettes



Dec. 21, 1965 w. R. MAHONEY ETAL 3,224,453

FILTER CIGARETTES Original Filed June 12, 1959 5 Sheets-Sheet 1 Dec. 21,1965 w. R. MAHONEY ETAL 3,224,453

FILTER CIGARETTES Original Filed June 12, 1959 3 Sheets-Sheet 2 Dec. 21,1965 w. R. MAHONEY ETAL 3,224,453

FILTER CIGARETTES 3 Sheets-Sheet 5 Original Filed June 12, 1959 DEYs/Ty( m s./c.c)

Ti :1 l E United States Patent 3,224,453 FILTER CIGARETTES William R.Mahoney, Pensacola, Fla., and Richard E. St. Pierre and Donaid T.Dunlap, Charlotte, N.C., assignors to Qelanese Corporation of America,New York, N.Y., a corporation of Delaware Original application June 12,1959, Ser. No. 820,041, now Patent No. 3,103,220, dated Sept. 10, 1963.Divided and this application Apr. 8, 1963, Ser. No. 271,057 The portionof the term of the patent subsequent to May 8, 1979, has been disclaimed3 Claims. (Cl. 131-208) This application is a divisional of applicationSerial No. 820,041 filed June 12, 1959, now US. Patent No. 3,103,220,which is a continuation-in-part of application Serial No. 714,634 filedFebruary 11, 1958, now US. Patent No. 3,032,829.

The present invention relates to a voluminous mass or tow of filamentarymaterial suited for making cigarette filters and other uses.

Voluminous or bulked filamentary tows or bundles of filaments are usefulfor a variety of purposes such as making efiicient cigarette filters,making wool-like or bulky textiles, and the like. Cigarette filters aregenerally formed of a multiplicity of crimped filaments, starting with acrimped tow or bundle of several thousand continuous filaments. Asreceived from the tow producer, the filaments may be more or lessadhered to each other with the crests and vales of adjacent filaments inregistry. The tow is passed through an air spreader, is fed by drivenrolls through a chamber in which plasticizer is applied, and it isthereafter condensed to equal approximately the cross-sectional area ofa cigarette. The condensed mass is formed into a coherent structure suchas by wrapping in paper and/ or curing and is cut into suitable lengthsfor incorporation into cigarettes.

In commercial operation it has been found that the filters so producedare not all identical in their filtering action. Specifically, it hasbeen found that the filters occasionally differ in weight, in filteringefiiciency and in the ease of draw, i.e. resistance to gas flow. Inaddition, after smoking many filters show uneven darkening whichindicates non-uniform passage of smoke therethrough, the darkened areasidentifying zones through which the smoke was preferentially drawn.

For producing bulky textiles, a continuous filament yarn may be passedthrough a turbulent zone of pressurized fluid, being dischargedtherefrom along with the fluid. The yarn is taken up at a slower speedthan it is fed and is characterized by high bulk. While the product isgenerally satisfactory, the process entails the use of large volumes ofpressurized fluid.

It is accordingly an object of the present invention to providedifferent types of bulked or voluminous tows or bundles of filaments.

It is a further object of the invention to provide improved voluminizedtows and improved cigarette filters produced therefrom.

Another object is to provide procedures for producing such improvedvoluminized tows.

Other objects and advantages will be apparent from the followingdetailed description and claims.

Our investigations have revealed that a major cause of irregularities inthe filter tips and their filtration characteristics can be traced tothe procedure for opening of the tow. Specifically, in the crimping ofthe tow all of the filaments are simultaneously acted upon and it willbe found that the crimps of adjacent filaments are in registry; if suchcrimp registration is not done away with there will be channels in thefilter through which smoke can pass without contacting any filamentsurface. In addiice tion, as produced, the tow may contain individualfilaments or groups of filaments which do not extend longitudinally butrather which extend at an appreciable angle transversely of the tow. Inprocessing, these transversely extending filaments or cross-overs tendto prevent those filaments which they overlie from being spread apartlaterally.

If a tow has not been evenly crimped initially, the tow openingprocedure may result in uneven application of plasticizer andthis inturn may result in uneven density with channeling of smoke through thefilter.

In accordance with one aspect of the present invention the tow is openedby passage over a ridge which is inclined to the path of movement of thetow. Conveniently the tow is passed between several pairs of opposedridges, at least one ridge of each pair being inclined to the path ofmovement of the tow, preferably both being inclined in differentdirections. This can readily be achieved by passage between a pair ofopposed ridged surfaces, the ridges of one surface being displacedlaterally relative to the ridges of the other surface, thereby laterallydisplacing some of the filaments relative to other of the filaments andthus opening the tow. Preferably the ridged surfaces are constituted bya pair of opposed grooved or ridged cylindrical rolls which arepositioned close to one another and rotate upon passage of towtherebetween. The surfaces are so formed that the ridges of one surfacewill not always be in registry with the grooves of the other surface.

A suitable configuration of ridges is created by forming a helicalthread in an elastic, e.g. rubber, or elasticsurfaced cylindrical roll.Advantageously both rolls are threaded in the same direction so that asthey rotate in opposite directions the ridges of one roll will not be inpermanent registry with the grooves of the other roll. By way ofillustration, at a given time a point on one ridge of one roll willcontact some point on a ridge of the other roll and as the tow advancesthe rolls will rotate and the points on the rolls where they werepreviously in contact will be displaced laterally relative to eachother.

If the opposed rolls are oppositely threaded, then their pitches,circumferences or rotational speeds should be different so that therewillnot be permanent registry between the ridges and grooves of therolls, i.e. so that points on both rolls where they are in contact willbe laterally displaced relative to each other.

Each helical roll will tend to displace the tow laterally in thedirection of advance of the helix, considering its direction ofrotation, e.g., if a helically grooved roll, on which the thread asviewed from one end advances in clockwise direction, is rotated incounterclockwise direction a tow contacting the roll will tend to bedisplaced away from the viewer. Where the other roll is similarlythreaded but rotates in opposite direction the tow will tend to bedisplaced toward the viewer. Both of these simultaneously actingtendencies further aid in opening the tow.

Conveniently, each roll is threaded from one end to its center in onedirection, e.g. clockwise, and from its other end to its center in theopposite direction, e.g. counterclockwise. Two such rolls are assembledwith their clockwise-threaded sections opposite each other and withtheir counterclockwise-threaded sections opposite each other. One of therolls will thus tend to condense laterally a tow fed near its middlewhile the other roll will tend to expand the tow laterally.

The ridged opening surfaces can be incorporated directly into existingapparatus for forming cigarette filters from tow, including an airspreader, if desired. After passing between the ridged surfaces the towis passed between a pair of braking rolls and then between a pair ofdriven rolls. The tow is thus tensioned between the driven and brakingrolls, the tension temporarily pulling out the crimp and making it moreregular upon subsequent r'elaxation. If desired, the braking rolls maybe omitted, their function being performed by the ridged openingsurfaces. Following passage between the driven rolls, which operate atconstant speed, the tow is advantageously passed through an airspreader, sprayed in relaxed condition with a plasticizing agent andconveyed to convent-ional condensing equipment to be formed into rodsfor incorporation into cigarettes as filter plugs.

In place of two opposed helically ridged cylindrical surfaces, one ofthe surfaces can be provided with circular or elliptical ridges.Alternatively, both surfaces may be provided with elliptical rings whichare either oppositely canted or arranged at different angles relative totheir respective axes so that the ridges on one cylinder will not alwayslie in registry with the grooves of the other cylinder. A similar effectwill be achieved using one cylinder with circular rings and another withelliptical rings.

In another embodiment, in place of providing the ridges on a pair ofcylindrical surfaces, one or both of the surfaces may be fiat and theridges can be shaped as they would appear if the rubber covering wereremoved from the cylindrical roll and were laid flat.

The ridges of one of the opposed surfaces can be registered with thegrooves of the other surface in one position but, as noted, should notbe in permanent registration. Thus, circular rings on both cylindricalrolls or straight parallel ridges on both opposed fiat surfaces can beemployed provided the registry is interrupted as by oscillating one orboth surfaces laterally out of phase with or in opposite direction tothe other surface. While circular rings are parallel to the direction ofadvance of the tow, such oscillation effectively inclines the rings soas to produce the effect of elliptical rings.

The tow is preferably composed of a plurality of crimped continuousfilaments of an organic derivative of cellulose, e.g. esters or ethersof cellulose such as cellulose acetate, cellulose propionate, celluloseacetate propionate, highy esterified cellulose containing less than 0.29free hydroxyl groups per anhydroglucose unit such as cellulosetriacetate, and the like. Other filamentary materials such as rayon(regenerated cellulose), linear superpolyamides such as nyon-6 andnylon-66, linear polyesters, acrylonitrile polymers and copolymers, andthe like, can also be employed.

The identity of the plasticizer will of course depend upon thecomposition of the tow. With cellulose acetate there may be employedtriethyl citrate, dimethoxy ethyl phthalate and methyl phthalyl etherglycolate but glycerol triacetate (triacetin) is preferred.

With tows opened in conventional manner there will still be appreciableregistry among adjacent crimped filaments which is aggravated at lowdeniers. By contrast, in accordance with the present invention thedenier of the individual filament may be as little as 2, although 17 ormore is also possible. Even with small deniers below about 7 theextensive opening and deregistry prevents channeling of the smoke sothat such low deniers are permissible. At the same time the low denierfilaments provide a greater surface area. In addition, they produce firmfilters which can be cured with less plasticizer with attendant savingsin time and material. Even at low plasticizer levels the novel plugswill be as firm as conventional plugs having much greater plasticizercontent. Firmness is measured by permitting a 4-ounce load knife edge torest transversely of a paper-wrapped filter plug for 10 seconds. Thepercent firmness is 100 times the height of the plug at the base of thedepression divided by the original diameter of the plug. The percentcompressibility is 100percent firmness. Generally the firmness of asatisfactory cigarette filter comprising a cured plug is at least about75% and preferably at least about 80%.

Whereas with conventional plugs this requires a relatively highplasticizer content, with the novel plugs equal firmness can be achievedat plasticizer contents of about 10% and preferably 7% or even less.

The filtration efficiencies of filters prepared from the novel tow aregreater than those of filters prepared from conventionally opened tow.As a corollary, the efiiciency of conventional filters can be duplicatedat lower plug weights and/or with less resistance to draw, i.e. lowerpressure drop. The total number of filaments may be as much as 120,000or more, preferably about 3,000 to 60,000, and the total denier may beabout 40,000 to 120,- 000 or more, preferably about 60,000 to 80,000.

The number of crimps per inch in the tow can range up to about 20 butpreferably averages between about 4 and 12. After leaving the drivenrolls the tow is still crimped but is about 10 to 200%, and preferably50 to longer than initially, i.e. the tow has been stretched so that thedistance between the crests of adjacent crimps has been increased andthe amplitude reduced. In addition, the crimps are deregistered and moreregular than initially.

With tows opened in conventional manner filters produced therefrom willexhibit reduced pressure drops and filtration efficiencies as the weightis decreased for a given tow specification, i.e. as for a given numberof filaments the stretch is increased to decrease the weight of tow in aplug of given length. If the plug weight is decreased too much, however,a limp useless plug will result. In accordance with the presentinvention it has also been found that the pressure drop and smokeremoval or filtration efiiciency generally decrease with decrease in theplug weight. Surprisingly, however, a plug weight is reached which whenfurther decreased produces an increased pressure drop and smoke removalefficiency. The exact value for this critical weight will vary,depending upon the constitution of the tow, i.e. crimp, denier perfilament and total denier, but generally lies in the neighborhood ofabout 0.18 gram per 15 mm.

In accordance with another aspect of the invention, the tow fed to theridged surface may comprise relatively few filaments. The tow may be fedand taken up as a yarn of little or no twist, without having previouslybeen partially opened. The yarn is voluminized or bulked in a mannersomewhat resembling crimping, except that the filaments are not lightlyadhered to one another as when employmg a conventional stufling boxcrimper. The voluminizing is even and regular with no filament extendingstraight for any appreciable distance. The degree of voluminizmg Wllldepend upon the arrangement of the ridges.

In accordance with another aspect of the invention, the openedvoluminous tow may be employed as a bottle wadding, padding or stuflingmaterial, in which capacities its high bulk results in decreased weightand material expense. The use of continuous filament material alsofacilitates handling since there are no short lengths of staple fibersflying about and adhering electrostatically to equipment. In addition,desired quantities can readily be severed with accuracy since the weightper unit length of the opened tow is quite uniform. Storage and shippingcosts are also reduced since the tow can be handled in dense bales andwill be opened only immediately priorto use.

A stuffing material can also be produced from opened tow which,advantageously without plasticization, is continuously formed into apaper-wrapped rod and severed into lengths which may be the same as ordifferent from the length of cigarette filter plugs. The ends of suchplugs are treated with solvent, plasticizer or heat to fuse the fibersand the wrapping is then removed to allow the coherent mass to balloonlaterally.

The invention will now be described more fully with reference to theaccompanying drawing, wherein:

FIG. 1 is a schematic elevation of a tow opening appa ratus inaccordance with the present invention;

FIG. 2 is a schematic elevation of a modified tow opening apparatus;

FIG. 3 is a lateral elevation of the helically threaded tow openingrolls of FIG. 1;

FIG. 4 is a section through a portion of one of the rolls taken alongline 44 of FIG. 3;

FIG. 5 is a lateral elevation of another pair of tow opening rolls whichcan be employed in the practice of the present invention;

FIG. 6 is an elevation of a pair of ridged flat plates which can besubstituted for the ridged rolls of FIG. 1;

FIG. 7 is a plan view of one of the plates of FIG. 6;

FIG. 8 is a perspective view of a cigarette, with the wrapper partiallytorn away, including a novel filter;

FIG. 9 is a view of a yarn produced in accordance with the invention;

FIG. 10 is a schematic perspective view of an apparatus for treating theopened tow;

FIG. 11 is a perspective view of a bottle containing a short length ofthe product of the apparatus of FIG. 10; and

FIG. 12 is a graph showing smoke removal efficiency plotted againstdensity for plugs in accordance with the invention.

Referring now more particularly to the drawing wherein like numeralshave reference to the same element, in FIG. 1 there is shown a bale 11of a multifilament tow 12, which tow is passed through an air spreader13 comprising a pair of spaced plates provided on their opposed faceswith longitudinal slits through which compressed air is directed againstthe tow.

From the air spreader 13 the tow 12 is drawn between rolls 14, 14 eachof which is elastically surfaced as at 15. The rolls 14 have theconfiguration shown in FIGS. 3 and 4 and described more fullyhereinafter. A yoke 16 determines the spacing between the rolls 14 andin cludes means for oscillating the rolls 14 in opposite directionsperpendicular to the plane of the drawing although preferably the rollsare not oscillated but are merely supported for rotation. The tow 12 isthen drawn between rubber braking rolls 17 which may be driven or whichmay be idly mounted for rotation.

The tow 12 then passes to positively driven rolls 18 which are alsoelastically surfaced and supply the force necessary to draw the towalong. These rolls 18 operate at a constant speed attuned to theoperating speed of the cigarette making machinery. If the braking rolls17 are positively driven, they are driven at a slower speed than rolls18 so as to exert a braking action on the tow.

The tow passes through another air spreader 19 and enters a plasticizingchamber 20 wherein there is provided a mist of plasticizer. Theplasticized tow upon emerging from chamber 20 is now in condition forpassage to rod-forming equipment (not shown) in order to be formedcontinuously into cigarette filter piugs. Although the tow 12 is nowrelaxed the spacing between crests of adjacent crimps is greater than itwas initially.

Filter rods and plugs formed from the tow are characterized byuniformity in weight, filtering characteristics and density. Smokepassing therethrough is not channeled as can be seen from the absence ofunevenly discolored areas at the end of the filter. The plugs are firmand the paper wrapping does not wrinkle, indicating a tight uniformpacking. These advantages are noted even when the original tow wasirregularly crimped and contained many cross-overs.

As shown more clearly in FIGS. 3 and 4, the rolls 14 as viewed from theright-hand side are helically threaded for half their lengths incounter-clockwise direction and for the other half in clockwisedirection. The base of each groove is V-shaped whereas the tops of theridges separating adjacent grooves are slightly flattened. In operation,the rolls 14 are moved closer toward each other, the distance being setso that the predetermined speed of driven rolls 18 will result in a towhaving the desired percent crimp, i.e. the rolls 18 are driven at theselected speed and the rolls 14 are moved toward each other until thetow emerging from between rolls 18 has the desired properties. The forceof rolls 17 against each other may also be varied to avoid undulyincreasing the spacing between rolls 14 which might reduce the openingaction. The rolls 14 may also be reciprocated in axial direction to aidin opening.

The rolls 14 rotate in the direction indicated by the arrows and it willbe seen that the upper roll will tend to reduce the width of the towpassing therebetween while the lower roll will tend to increase thewidth of the tow. In practice it has been found that with identicalrolls grooved as shown the lower roll apparently exerts a greaterinfluence so that there is a net increase in width of the tow.

The modified apparatus shown in FIG. 2 is dentical with that of FIG. 1except that the braking rolls 17 have been omitted. In this embodimentthe grooved rolls 14 take over the braking function to control thestretching of the tow. Control over the uniformity of crimp, i.e.uniformity of tow density in longitudinal direction of the tow, is lessexact but if a regularly crimped tow is initially employed the productwill be almost as uniform as that produced by the apparatus of FIG. 1,whereas the apparatus of FIG. 1 will give excellent results with towswhich are regularly crimped, e.g. by toothed gear wheels, as well aswith more randomly crimped tow.

In place of a pair of rolls 14 which are helically threaded in oppositedirection from each end, each roll may be threaded only in onedirection. Alternatively, as shown in FIG. 5, one roll 21 may beprovided with parallel circular ridges or rings 22 each extending in aplane perpendicular to the axis of the roll 21 while the other roll 23is provided with parallel elliptical ridges or rings 24 each extendingin a plane inclined relative to the axis of roll 23. It is apparent thatupon rotation there will be relative lateral movement between the ridges22 and the ridges 24. This will also be achieved if either roll 21 or 23is used in conjunction with one roll 14, if two rolls 23 are used withtheir ridges inclined in opposite directions, if two rolls 21 are usedand one is reciprocated laterally relative to the other, etc.

FIG. 6 shows a pair of plates 25 which can be substituted for the rolls14. In use the plates may be reciprocated laterally but they arepreferably stationary. Each plate 25 has a ridged surface and as can beseen in FIG. 7 the surface has the appearance which would result fromcutting rubber covering 15 of roll 14 parallel to the roll axis andflattening out the covering.

In FIG. 8 there is shown a cigarette comprising an outer paper wrapping26 enclosing tobacco 27 and a filter composed of a paper wrapper 28surrounding filaments 29. The filter comprising wrapper 28 and filaments29 may be made by wrapping tow 12 with paper in conventional manner asit leaves plastieizer chamber 20 (FIGS. 1 and 2), cutting it intopredetermined lengths (not shown) and curing. To the naked eye thefilter will look the same as conventional filters, but it will feel morefirm than conventional filters of equal filament and plasticizercontent. If the filter is broken apart, or if the tow is examined as itleaves rolls 18 it will be apparent that the tow is more voluminous thantows of the same number of filaments and total denier which have notbeen passed between ridged rolls 14. In addition, there will be butlittle registry in the crimps of adjacent filaments.

The yarn 30 shown in FIG. 9 comprises many filaments which appear to bevoluminized in more or less registry. The filaments, however, areindividual rather than lightly adhered as when crimped in conventionalmanner.

In place of being plasticized and formed into cigarette filter plugs, asshown in FIG. 10, the opened tow 31 can be cut by cutter 32 intopredetermined lengths 33 suited for stuffing, padding or bottle wadding.Because of their open structure, lengths 33 fill out any space intowhich packed. They are free of short fibers which can work their wayloose, thereby eliminating the problems and inconveniences attendingsuch loose particles. In addition, they are clean, highly absorbent andinert. FIG. 11 shows such a mass 33 stuffed into a bottle 34 containingmaterial such as aspirins 35, the mass 33 keeping the aspirins frommoving about or becoming soggy and losing their individual shapes oridentities.

The following examples are given to illustrate this invention further.

' EXAMPLE I (a) Using the apparatus shown in FIG. 1, an 80,000 deniertow of 20,000 cellulose acetate continuous filaments, averaging 8 crimpsper inch, is passed through air spreader 13 and is subjected tocompressed air at 3 p.s.i.g. The tow passes between grooved rolls 14which are 14 inches long and 5.5 inches in diameter, eighteen helicalthreads per inch being cut about inch deep into the rubber covering.Next, the tow passes between braking rolls 17, idly mounted for rotationand forced against each other sufficiently hard to require a force of 15pounds to pull the tow manually therethrough. Driven rolls 18 arerotated at a peripheral speed of 37.25 yards per minute and the towpicks up 7% of its weight of triacetin in chamber 20. The tow leavingchamber 20 is wrapped with paper on conventional cigarette makingequipment and cut into 15 mm. lengths which are cured for 24 hours atroom temperature. One hundred such plugs are tested for weight, pressuredrop and smoke removal efficiency. The pressure drop is the suctionnecessary to maintain a flow rate of 17.5 cc. of air per second throughthe plug, not incorporated into a cigarette. In determining smokeremoval efliciency, 12 puffs of 35 cc., i.e. 2 seconds of pufiing, aredrawn from a lit cigarette through the filter and through a trap havingon its bottom a sintered glass disk. 2 grams of sifted alpha celluloseare placed on the disk, producing a pressure drop of about 5 centimetersof water. The trap is immersed half way in a Dry Ice-acetone bath. Theformula for the smoke removal efficiency is as follows:

A Weight of filters A wt. of filters+A Wt. of trap Percent efiicieney X100 EXAMPLE II (a) The process of Example I(b) is repeated with a towmade up of 21,000 of the same filaments. The plugs weigh 0.188 gram,have a pressure drop of 62.1 mm. H 0 and a smoke removal efficiency of15.1%.

(b) Inserting the grooved rolls into the process of Example II(a) andincreasing the stretch, the plugs weigh 8% less. While the pressure dropof the well-opened tow goes up 4%, the smoke removal efiiciency goes up42%.

While the extensive opening of the tow resulted in a somewhat increasedpressure drop for the novel filters, it will be noted that the percentincrease in smoke removal efliciency exceeded the percent increase inpressure drop g a X 100 =percent increase) EXAMPLE III ing weight. Theresults of tests on weight, pressure drop and smoke removal efficiencyof 13 mm. plugs are given in the following table. The weight in gramsset forth in the table below is for a constant volume of about 0.649cubic centimeters which is the standard cigarette filter volume.

Table Weight, Pressure Smoke Density Run Grams Drop, Removal, (gms/cc.)

mm. H O Percent It can be seen that as the plug weight decreasesinitially, the pressure drop and smoke removal efficiency also decrease.In reducing the plug weight going from Run 3 to Run 4 surprisingly thesmoke removal efficiency increases. In going on to Run 5 it is foundthat although the weight is less both the pressure drop and smokeremoval efficiency are greater than in Run 3. This effect is furtherevidenced in Run 6.

FIG. 12 shows the curve obtained by plotting the smoke removalefiiciency of these runs against density. Consideration of the graphpoints out that as the density decreases, the smoke-removal efliciencydecreases but that this reaches a minimum and thereafter a decrease infilterplug density results in an increase in smoke-removal efficiency.

EXAMPLE IV Using the grooved rolls shown in FIG. 1 a cellulose acetateyarn composed of 240 4-denier filament united with 4.5 Z turns per inchare pulled between the grooved rolls by rolls driven at 37.25 yards perminute, emerging from the driven rolls as a crimped yarn.

EXAMPLE V The same tow used in EXAMPLE I, after leaving rolls 18, is cutinto 1 centimeter length used as a wadding in medicine bottles.

It is to be understood that the foregoing detailed description is givenmerely by way of illustration and that many variations may be madetherein without departing from the spirit of our invention.

Having described our invention What we desire to secure by LettersPatent is:

1. A plug of substantially uniform cross-sectional density for cigarettefilters comprising a tow of about 3000 to 120,000 crimped continuousfilaments of less than about 25 denier per filament, the crimps of saidfilaments generally being out of registry with one another, said crimpshaving been deregistered by a method comprising longitudinally movingthe tow having filaments the crimps of which are generally in registry,while contacting the tow with at least one ridge, said ridge beinginclined to the path of movement of the tow, thereby to displace some ofthe filaments of the tow relative to other filaments of the tow wherebythe crimps of the filaments are generally moved out of the registry,said plug having a density less than about 0.23 gram per cubiccentimeter and a smokeremoval efficiency of at least about 15%.

2. A plug of substantially uniform cross-sectional density as claimed inclaim 1 wherein said filaments are cellulose acetate.

3. A plug of substantially uniform cross-sectional density for cigarettefilters comprising a tow of crimped continuous cellulose acetatefilaments, the crimps of said filaments generally being out of registrywith one another,

said crimps having been deregistered by a method comprisinglongitudinally moving the tow having filaments the crimps of which aregenerally in registry, while contacting the tow with at least one ridge,said ridge being inclined to the path of movement of the tow, thereby todisplace some of the filaments of the tow relative to other filaments ofthe tow whereby the crimps of the filaments are generally moved out ofregistry, said plug having a density less than aobut 0.23 gram per cubiccentimeter and a smoke-removal eflieiency of at least about 15%.

References Cited by the Examiner UNITED STATES PATENTS SAMUEL KOREN,Primary Examiner.

10 MELVIN D. REIN, Examiner.

1. A PLUG OF SUBSTANTIALLY UNIFORM CROSS-SECTIONAL DENSITY FOR CIGARETTEFILTERS COMPRISING A TOW OF ABOUT 3000 TO 120,000 CRIMPED CONTINUOUSFILAMENTS OF LESS THAN ABOUT 25 DENIER PER FILAMENT, THE CRIMPS OF SAIDFILAMENTS GENERALLY BEING OUT OF REGISTRY WITH ONE ANOTHER, SAID CRIMPSHAVING BEEN DEREGISTERED BY A METHOD COMPRISING LONGITUDINALLY MOVINGTHE TOW HAVING FILAMENTS THE CRIMPS OF WHICH IS GENERALLY IN REGISTRY,WHILE CONTACTING THE TOW WITH AT LEAST ONE RIDGE, SAID RIDGE BEINGINCLINED TO THE PATH OF MOVEMENT OF THE TWO, THEREBY TO DISPLACE SOME OFTHE FILAMENTS OF THE TOW RELATIVE TO OTHER FILAMENTS OF THE TOW WHEREBYTHE CRIMPS OF THE FILAMENTS ARE GENERALLY MOVED OUT OF THE REGISTRY,SAID PLUG HAVING A DENSITY LESS THAN ABOUT 0.23 GRAM PER CUBICCENTIMETER AND A SMOKEREMOVAL EFFICIENCY OF AT LEAST ABOUT 15%.